Shock Pulse - Living Lightning is an awesome signature spell for Archon downtime in combination with some crit chance and CM.Quote from Bagstone
I'd second the idea of getting Lacuni's. For chest, look out for a decent Tal Rasha - but later, when you have more money. Since you have a purely physical damage weapon, maybe you can even upgrade your offhand with a Triumvirate for some money; you could get rid of the APoC and switch to a signature spell for Archon downtime or keep the Oculus and switch OH on cooldown.
A good Triumvirate with 6% to at least 2 damage types, some good average damage and max crit should be easy to get for 1-2m, if you're lucky you might even be able to get some int on it. It gives an absolutely insane damage boost if you don't need APoC.